Earth-boring tools for forming boreholes in subterranean earth formations, such as for hydrocarbon production, carbon dioxide sequestration, etc., generally include a plurality of cutting elements secured to a body. For example, fixed-cutter earth-boring rotary drill bits (also referred to as “drag bits”) include cutting elements fixed to a bit body of the drill bit. The cutting elements may be affixed to blades disposed along an outer diameter of the bit body.
Bit bodies and blades may be formed of metal-matrix composites having a continuous phase and a dispersed phase. The continuous phase may be a metal or an alloy, such as a copper alloy, steel, cobalt, a cobalt-nickel alloy, etc. The dispersed phase may be a reinforcing material, and may be a different metal or another material, such as a ceramic. The dispersed phase may be selected to impart a particular property to the composite, such as hardness, wear resistance, strength, thermal conductivity, etc. For example, the dispersed phase may include materials such as tungsten carbide, cubic boron nitride, silicon carbide, diamond, etc. The dispersed phase may include particles, fibers, whiskers, etc. Bit bodies and blades may also be formed from steel.
During drilling operations, drill bits may be subjected to harsh conditions, such as high temperatures, high pressures, and corrosive fluids. Under some operating conditions, hard formation material may cause deflection of blades, and may cause damage to blades. Various methods have been developed to prevent damage to drill bits during drilling. For example, wear-resistant inserts may be disposed on blades to stabilize the drill bit and control bit aggressiveness. Such inserts may cause blades to engage the formation material to a preselected depth. Limiting the depth of the formation engaged by each blade may limit the potential damage to the blade, but may also limit the rate of penetration (ROP) of the drilling operation.
U.S. Pat. No. 7,571,782, issued Aug. 11, 2009, and entitled “Stiffened Blade for Shear-Type Drill Bit,” the disclosure of which is incorporated herein in its entirety by this reference, describes a steel bit body with stiffening elements to increase the stiffness of the blades. The blades may be less susceptible to wear and damage than unstiffened blades, and the bit may have a longer service life. Stiffening elements may include, for example, backing plates, brackets, carbide segments, or carbide rods. Drilling with blades having high stiffness may cause a more uniform or constant impact of cutting elements on the formation. Thus, ROP may be increased, and damage to drill bits may be limited.